Mitchell is a train wreck during much of Book Two. He is addicted to cocaine, prescription drugs, and alcohol. In just a few years he squandered the millions of dollars he made from the sale of the house with his exorbitant drug debt and shady investments.
Mitchell is good-hearted, intelligent and cultivated, but is a victim of his demons. His third wife, Naiyana, is at the end of her rope when the Piersons meet her.
When Mitchell is arrested on cocaine charges, David bails him out and Mitchell stays at Beak's End while awaiting trial. Long suffering Naiyana returns to Australia, leaving the future of the marriage looking bleak. He is grateful for David and Lia's kindness, but refuses to allow anyone to get close to him, except for rare moments from which he immediately catches himself.
After he commits an egregious act against David and Lia, there is a sequence of events which culminate in their having a breakthrough on the mystery of Mitchell Mathers. Mitchell is biologically and spiritually a Ley.
By the end of Book Two, Mitchell is on the road to retrieving his true self, although still incarcerated.